Ore agglomerates and methods of making the same



United States Patent 3,382,063 ORE AGGLUMERATES AND METHODS OF MAKINGTHE SAME Louis George lmperato, Jr., Tenafly, N.J., assignor to BlockedIron Corporation, a corporation of New York No Drawing. Filed June 10,1964, Ser. No. 374,191 1 Claim. (Cl. 75-3) This invention relates to oreagglomerates and methods of making the same and particularly to a highstrength and at least partially self reducing iron ore agglomerates andmethods of making such agglomerates.

The need for a satisfactory method of agglomerating iron and other ores,particularly oxide ores, has long been recognized. As the high purity,lumpy ores of the Mesabi and other ranges have been exhausted it hasbeen necessary to turn to ore concentrates recovered from less pure oredeposits and to fine ores not heretofore considered suitable for steelmaking. In order to make these ores suitable for handling and use insteel melting furnaces it has been necessary to agglomerate these oresinto larger pieces. This has conventionally been done by pelletizing orbriquetting the fine ores and sintering or fusing the pellets orbriquettes to form the solidified agglomerates. Sintering requiresextremely high temperatures and large capital outlays in temperatureresistant equipment.

I have invented an ore agglomerate and method of making suchagglomerates which is much less expensive than these sinteredagglomerates and is at least partially self reducing.

In the preferred practice of my invention I admix ore fines with anoxide or hydroxide of an alkaline earth metal, a finely dividedcarbonaceous material and optionally with a small amount of a mineralacid salt of an alkali metal, or an alkaline earth metal and/or a smallamount of an alkali hydroxide together with suflicient water to permitthe formation of agglomerates such as pellets, briquettes or blocks.These agglomerates are then subjected to an atmosphere of carbon dioxidefor a time sufiicient to convert a major portion of the alkaline earthoxide or hydroxide to carbonate.

I have found that the moisture level for most eiiective operation of myprocess is below by weight of the total admixture and preferably in theneighborhood of 5% or less.

Preferably the carbonaceous material used in my process is finelydivided coal. I prefer the size range of 4 mesh and under for the coalused and good results have been attained at both ends of the range aswell as with mixtures of varying particle size coal. I have found thatamounts between about 5% to of coal by Weight are most satisfactory formy purposes, although larger amounts up to have been satisfactorily usedin practicing my process. I have found that the use of minus 100 meshcoal makes it possible to ball or pelletize conventional as receivedspecular hematite concentrate without the addition of reground hematiteor without the ad- 3,382,063 Patented May 7, 1968 dition of any otherfine ore. Prior to my invention, it had been impossible to form balls orpelletize specular hem-atite by usual balling or pelletizing methodswithout regrinding or adding another fine ore. This has been one of thevery real problems in the heat indurate types of pellets heretofore madeand is a very distinct advantage to be gained by the practice of thisinvention. I have found that this can be accomplished within the rangeof coal concentration set out hereinabove, although I prefer to useabout 10% minus 100 mesh coal when forming specular hematite balls orpellets.

The amount of alkaline earth oxide or hydroxide, e.g. lime, preferablylies in the range from about 5% to 20% by weight of the admixture.

I prefer to add a small amount (up to about 2%) of a solubilizing agentfor calcium and magnesium, as disclosed in my Patent No. 2,996,372, suchas a sugar containing material, e.g. blackstrap molasses, glucose,fructose, dextrose, syrups or the like together with a small amount of amineral acid salt of an alkali or alkaline earth metal such as calciumchloride in an amount less than about 1%. I may also add a small amountof an alkali metal oxide or hydroxide such as sodium hydroxide,preferably in the range of about 0.1% to about 1.5%.

The practice of my invention produces a resulting product which has highstrength after being subjected to elevated temperatures, e.g. 17001900F., and which shows a high percentage of reduced iron after such heatingindicating that the product is self reducing. Both of these propertiesare highly sought after and difiicult to achieve.

The practice of my invention can perhaps best be explained by referenceto the following examples which show the significances of the practiceof my invention.

Example I A series of tests were made on pellets produced by ballingspecular hematite as received and reground with high volatile coal andlow volatile coal and mixtures of the two types of coal, with lime andwith 0.5% blackstrap molasses and 0.4% calcium chloride. The coal wasused as received in which condition its size was minus 4 mesh andreground to 100 mesh (100 M). The lime was a mono hydrated dolomiticlime powder known in the trade as Ohio Super spray hydrate.

A series of tests to determine the green ball strength andcharacteristics were performed as follows.

Drop test.-A representative sample of twenty carefully sized green Wetballs are dropped individually from a height of eighteen inches onto asteel plate and the number of consecutive drops required for failure isused to determine an arithmetical average.

Green ball compression test-An identical sample as just previouslydescribed is used and a compressive load is applied to individual ballsand the load required to fracture is used to determine the arithmeticalaverage.

The resulting data appear in Table I.

TABLE I.GREEN BALL STRENGTHS Specular Specular Coal, Hematite HematiteLime, Drop test, Compression, Coal, type percent cone. as cone.repercent drops to lbs. to failure received, ground, failure percentpercent None 71. 00 24. 00 5.00 6 2. 2 High volatile coal, as received9. 48 64. 10 21. 3O 5. 12 13 3. 3 High volatile coal, as received 100 M4. 67. 60 22. 54 5. 12 14 3. 3 D 9. 48 64.10 21. 30 5.12 16 4. 1 18. 9656. 96 18. 96 5.12 24 3. 4 25.00 52. 42 17. 46 5.12 40 3. 2 Low volatilecoal, as rec yo 9. 48 64. 10 21. 30 5. 12 16 3.1 Low volatile coal, asreceived M 9.48 64. 10 21.30 5. 12 18 4. 1 High volatile coal, 100 M11.00 83. 88 None 5. 12 13 3. 1 Do- 8.00 85.00 None 7.00 19 3. 6

3 Example 11 The pellets of Example I were treated with carbon dioxideat room temperature to harden and convert the lime to carbonate in situ.These hardened pellets were tested as 4; a period of two hours afterwhich the specimens are removed and a qualitative observation of theircondition is noted.

Crucible test.Carefully sized 13/32 +12/32" follows 5 pellets are placedfour at a time in a coal filled crucible,

I covered and then heated by an ignited Fisher burner for a p 5 32 21:$25; 3 fi g gg ig iil i igi gsg g igg predetermined period after whichthe pellets are removed residue remaining on a screen after 280revolutions s. g i to return i g i g? benig is recorded as a percentageof the original five pounds and i J o comPresslye es 0 es me 15 eye 6noted as the tumble strength index 10 is repeated for venoustime/temperature cycles as noted for each run.

Reduction test.-Pellets which had been heated in the above describedcrucible test are placed in a magnetic field and the degree ofattraction is recorded as a qualitative observation.

Compression test.A representative sample of twenty pellets are drawn anda compressive load is applied to individual pellets and the loadrequired to fracture is used to determine the arithmetical average.

The results of these tests are tabulated in Table II.

) TABLE II.-ROOM TEMPERATURE STRENGTH DATA ESipecular ematite Coal,Taeonite, Lime Compres- Tumble test percent Coals, type cone, percentpercent Hydrate, sion test, 0/0+%" as receivedpercent lbs. 280 Rev.

reground High volatile -100 M 67. 60-22. 54 5. 12 320 90 do 64.10-21. 5.12 225 60 do 56. 92-18. 96 5. 12 105 96 do 52. 42-17. 46 5. 12 96 Lowvolatile l00 M. 64. 10-21. 30 5.12 170 99 9.48... High volatile, asreceived- 64. 10-21. 30 5. 12 250 99 9.48 Low volatile. as received" 64.10-21. 30 5.12 225 98 84. 00-0 6. 00 260 98 6. 30 343 96 9. 10 445 5.00205 G. 00 255 90 d 7. 00 323 9.48 50/50 h h v0lati1e/-100 low volatile.64. 10-21. 30 5.12 205 99 9.48 50/50 as received high volatile and lowvolatile..." 64. 10-21. 30 5. 12 240 98 The results appear in Table III.

TABLE III.CRUCIBLE TEST DATA Specular Taco- Crucible testload tofailure, lbs. after Hematite nite, Lime time in minutes Coal,percent-type cone, percent perhydrate,

as receivedcent percent 0 15 30 45 210 reground None 72-23 5.00 410 2314 9 8 11 12 4.74-high volatile M.-." 67. 6-22. 54 5. 12 320 30 30 29 2929 27 Heat indurate taconite pellet 500 23 15 16 19 12 18 9.48-highvolatile as received" 64.1-21.3 5. 12 250 27 27 24 22 22 19 9.48-l1ighvolatile 100 M 64. 1-21. 3 5. 12 225 30 30 30 3O 29 21 Do 34. 2-51. 205. 12 180 30 30 30 30 30 27 0.48-low volatile as received. 64.1-21.3 5.12 30 25 21 20 20 17 18.96-high volatile -100 M 56. 96-18. 96 5.12 30 2323 17 15 10 11.00-l1igh volatile 10O M- 83.88 5. 12 30 28 23 20 19 1213.00-high volatile 100 M 81. 88 5. 12 135 30 30 29 25 22 16 None 70.0-23. 5 6. 50 500 30 26 23 16 19 17 10.00-h1gh volatile -100 M 4. 0 6.0030 30 30 30 26 18 Do 83. 0 7.00 178 30 30 30 30 28 22 None. 57.00-38.001 5. 00 11 5 8 8 8 9 9 948-..... 51.2-34.2 5.12 5 5 3 2 2 3 3 None 60-4010 2 2 2 2 2 2 Non-carbonated. 2 None (non-carbonated) (0.75 bentonite).

Example III The carbonated pellets of Example 11 were tested at elevatedtemperatures and in reducing atmospheres as follows and compared to acommercial taconite heat indurate Example IV Pellets were made as inExample II by carbonation substituting taconite concentrates for thespecular hematite. These pellets were subject to the same tests asExample pellet. 60 III and the data tabulated in Table IV.

TABLE IV Specular Taco- Crucible test-load to failure, lbs. afterHematite nite, Limo time in minutes Coal, percent-type cone, percentperhydrate,

as receivedcent percent 0 15 30 45 60 90 210 rcground None. 93.7 6.3 34330 30 30 30 30 30 5.00-hlgh volatile 100 M 88.0 7. 0 323 50 40 30 30 3030 None 93. 28 1 6. 72 10 16 25 28 20 13 19 9.48-high volatile 100 M 83.80 1 6. 72 7 8 7 9 7 6 8 1 Non-carbonated.

0 en flame tes .Selected ec' ns la n p t sp me are p ced o a EXAMPLE VNichrome wire mesh screen which is located (10) ten millimeters abovethe grid of an ignited Fisher burner and Pellets were made by admixinglime hydrate, coal and the resultant flames are allowed to envelop thesample for 75 ore as in Example I. The resulting pellets were subjected5 d to carbon dioxide sutlicient to form recrystallized liine- EXAMPLEVI stone in situ. The carbonated pellets were then divided into tWoparts, one heated to 1600 F, and the other to An additional series ofpellets were made as in Example 1700" F. in an atmosphere containingcarbon monoxide V and after removal from the heating furnace at 1600-such as would be encountered in a blast furnace or like i 5 and 17000 pyi w Scieeiled t (letemllfle iron handling furnace, Th pgllets wereremoved and Th6 amount above 4 mesh and U16 amount below 20 mesh.analyzed for reduced iron, The results ar tabulated in They were thenjarred for minutes in a container and Table V. again screened. The testresults appear in Table VI.

TABLE VI Screen Test From Furnace Screen Test After Jar-ring 16,000" 11,700 F. 1,600 F. 1,700 F.

M +4 M M +4 M 20 M +4 M 20 M +4 M -20 M 'Iacenite:

6% Lime Hydrate 96. 7 1. 67 96.9 1. 48 43. 7 51.3 9% Lime 1l arii:e 99.90.1 99.87 0.13 77. 82 21. 96 78. 2s 21. 02 12% Lime Hydrate 99. 6 0. 399. 5 0. 2 e3. 9 15. 9 82.8 16. s 9% Lime Hydrate plus 10% High VolatileGoal (-8 M) 99. 2 0. 38 97. 6 0. 13 80. 64 17. 80. 09 15. 0 9% LimeHydrate plus 8% High Volatile Goal (-8 M) and 2% Low Volatile Goal (-8M) 62 0. 61 99. 47 0. 23 81.00 16. 98 84. 17 14. 24 9% Lime Hydrate plus8% High Volatile Coal (8+150 M) and 2% Low Volatile Coal (-8+150 M) 96.69 0. 56 98. 57 0. 42 81. 77 14 23 78. 77 17. 37 Specular Hematite: 25%Rcground 325 M) plus 5% Lime Hydrate plus 15% High Volatile Goal (-100M) 0. 96. 80 2. 54 76.77 20 17 57.12 36. 61 Venezuelan Ore:

Plus 4.76 Liine Hydrate. 97.59 0.87 60.43 32. 41 6% Lime Hydrate plus15% High Volatile Goal (-100 H) .2 98. 0 1 0 2. 0 85. 11v 79 84. '75 1282 TABLE V--CARBONATE BONDED PELLET SUMMARY It will be evident from theforegoing tables and exampemem Reduction ples that a high strengthpellet capable of a high level R 30 of selt reduction can be achieved bythe practice of my T C t lnvention.

23}; 38-7 4L8 While I have described certain preferred practices andLime Hydrate... ime Hydrate L me Hyd rgte plus 5 High Volai;

- products according to my invention, it will be understood 5 that thisinvention may be otherwise embodied Within Goal (-100 i 49.1 81.5 1

9% Lime Hydrate plus 8% High volatile 3.1 the scope of the followingclaim.

S 1CoaIl1Plust2%10w 'olattsile Goal -3 M) I claim:

pceu ar ema ite once lira e:

23.57 Reground (325 M) Specular ite 1 The method of producing a highstrength, self reg te lus 5%dL1ne II ra t LL LLL 39.3 45. 0 dueing lumpore from finely divided iron containing mal 1 e 50,6 7 terialscomprising the steps of admixing the finely divided P m yd t 39 8 40iron containing material with at least one of the group As ReceivedSpecular Hematite plus 5% consisting of the oxides and hydroxides oralkaline earth 625 Hydrate Plus 10% High volatile 49 1 87 1 metals andwith coal having a fineness of 4 mesh and venezuelaii'o'iei under,forming the mixture into lumps and reacting the Plus 15% High Volatile(331 lumps with carbon dioxide in the presence of moisture to 100M lus6LimeH drat )p y e 40 form alicaline earth carbonates in situ in thelumps.

References Cited UNITED STATES PATENTS 145,462 12/1873 Taylor 32,823,109 2/1958 Sudo 75-3 2,844,457 7/1958 Amberg 75-3 2,996,372 8/1961Iniperato 75--3 FOREIGN PATENTS 877,932 9/1961 Great Britain.

BENJAMIN HENKIN, Primary Examiner.

1. THE METHOD OF PRODUCING A HIGH STRENGTH, SELF REDUCING LUMP ORE FROM FINELY DIVIDED IRON CONTAINING MATERIALS COMPRISING THE STEPS OF ADMIXING THE FINELY DIVIDED IRON CONTAINING MATERIAL WITH AT LEAST ONE OF THE GROUP CONSISTING OF THE OXIDES AND HYDROXIDES OF ALKALINE EARTH METALS AND WITH COAL HAVING A FINENESS OF 4 MESH AND UNDER, FORMING THE MIXTURE INTO LUMPS AND REACTING THE LUMP WITH CARBON DIOXIDE IN THE PRESENCE OF MOISTURE TO FORM ALKALINE EARTH CARBONATES IN SITU IN THE LUMPS. 